CYCADALES 



141 



It is generally accepted that the cycads are wind-pollinated. 

 Pearson (47), however, observed insects dusted with the pollen of 

 Encephalartos villosus, and belie\'es it is probable that they effect 





Figs. 155-159. — Dioon edule; the germination of the microspore; fig. 155, the 

 nucleus in early prophase of the first mitosis, exine and intine sharply differentiated 

 (August 14, 1905); fig. 156, the shedding stage (September 1906); fig. 157, beginning 

 of the pollen tube; /, tube nucleusf g, generative cell; p, prothallial cell; fig. 158, 

 the generative cell divided (October 21, 1907), giving rise to stalk cell (s) and body 

 cell {b), no blepharoplasts visible; fig. 159, later stage (November 20, 1906), the body 

 cell much elongated and the blepharoplasts with very conspicuous radiations; figs. 

 155-157, Xi,26o; fig. 158, Xi,ooo; fig. 159, X630. — After Chamberl.aix (63). 



pollination. In Dioon edule (63), when the pollen is shed, a large 

 pollination drop oozes from the micropyle, just as in gymnosperms 

 which are known to be wind-pollinated, and in this case, also, insects 

 dusted with pollen were found in the staminate cones, but there was 

 nothing further to indicate that pollination was being effected through 



